Polishing pad and manufacturing method therefor

ABSTRACT

Provided are a polishing pad which remedies the problem of scratches occurring when a conventional hard (dry) polishing pad is used, which is excellent in polishing rate and polishing uniformity, and which can be used for not only primary polishing but also finish polishing, and a manufacturing method therefor. The polishing pad is a polishing pad for polishing a semiconductor device, comprising a polishing layer having a polyurethane-polyurea resin foam containing substantially spherical cells, wherein the polyurethane-polyurea resin foam has a hard segment content (HSC) in a range from 26 to 34%, and has a density D in a range from 0.30 to 0.60 g/cm 3 , the hard segment content (HSC) being determined by the following formula (1): 
       HSC=100×( r −1)×( Mdi+Mda )÷( Mg+r×Mdi +( r −1)× Mda )  (1).

TECHNICAL FIELD

The present invention relates to a polishing pad, and more specificallyto a CMP polishing pad for a semiconductor device.

BACKGROUND ART

Since surfaces of materials such as silicon, hard disks, mother glassfor liquid crystal displays, and semiconductor devices need to be flat,the surfaces are polished by the loose abrasive method using a polishingpad. The loose abrasive method is a method in which the work surface ofa workpiece is polished while a slurry (polishing liquid) containingabrasive grains is supplied between a polishing pad and the workpiece.

In a polishing pad for a semiconductor device, the surface of thepolishing pad is required to have openings for retaining abrasivegrains, rigidity for keeping the flatness of the surface of thesemiconductor device, and elasticity for preventing scratches on thesurface of the semiconductor device. As a polishing pad meeting theserequirements, a polishing pad having a polishing layer manufactured froma urethane resin foam has been used.

In general, a urethane resin foam is molded by curing a prepolymercontaining an isocyanate group-containing compound based on a reactionwith a curing agent (dry method). Then, a polishing pad is formed byslicing this foam into a sheet shape. In a polishing pad (hereinafter,abbreviated as hard (dry) polishing pad in some cases) having a hardpolishing layer molded by the dry method as described above, relativelysmall and substantially spherical cells are formed inside the foamduring the curing and molding of the urethane resin. Hence, openings(pores) capable of retaining a slurry during polishing are formed on thepolishing surface of the polishing pad formed by the slicing.

Urethane resin foams having cell (air-bubble) diameters of 100 μm orless and around 30 μm have been mainly used as materials of polishingpads for a semiconductor device so far (Patent Literature 1). Inaddition, the mainly used urethane resin foams have type A hardnesses of70 degrees or higher, and type D hardnesses of 45 or higher (PatentLiteratures 2 and 3). The mainly used urethane resin foams havedensities of 0.5 g/cm³ or higher (Patent Literature 1) and, regardingthe elasticity, have storage elastic moduli of several hundredmegapascals or higher (Patent Literature 4). A mainly employedlongitudinal elastic modulus (Young's modulus) is 500 MPa or higher(Patent Literature 5).

Apart from the above-described mainly used urethane resin foams,physical properties of urethane resin foams have been improved from theviewpoints of the bulk density, the type A hardness, and the hardsegment content (HSC) (%) in order to reduce wearing to an appropriatedegree and stabilize the polishing performance (Patent Literature 6).Moreover, polishing pads are also reported whose storage elastic moduliare adjusted to be within predetermined ranges in order to reduce theoccurrence of scratches (Patent Literatures 7 and 8).

CITATION LIST Patent Literatures

-   Patent Literature 1: Japanese Patent No. 4338150-   Patent Literature 2: Japanese Patent No. 3924952-   Patent Literature 3: Japanese Patent No. 3788729-   Patent Literature 4: Japanese Patent No. 3983610-   Patent Literature 5: Japanese Patent Application Publication No. Hei    10-6211-   Patent Literature 6: Japanese Patent Application Publication No.    2010-58194-   Patent Literature 7: Japanese Patent Application Publication No.    2006-11.4885-   Patent Literature 8: Japanese Patent Application Publication No.    2009-256473

SUMMARY OF INVENTION Object to be Solved

However, the above-described dry polishing pads are still hard, and tendto apply a pressure to a workpiece in a localized manner. Hence, the drypolishing pads are unsatisfactory in terms of reduction of polishingscars (scratches) formed on the surface of a workpiece. In addition, thedry polishing pads still have a problem of high possibility of clogging.For this reason, in general, after polishing with a hard polishing padmolded by the dry method, it is necessary to further perform finishpolishing by using a polishing pad having a soft polishing layer moldedby a wet method (in the wet method, a resin solution obtained bydissolving a resin in a water-miscible organic solvent is applied onto asheet-shaped film formation substrate, and then the resin is coagulatedand regenerated in an aqueous coagulating liquid).

On the other hand, a polishing pad having a soft polishing layer moldedby a wet method has a low hardness, has large openings of a suede type,and has a non-uniform foam structure. For these reasons, althoughpolishing using the polishing pad having a soft polishing layer achievesbetter polishing rate and polishing uniformity (uniformity:followability of the pad surface to waves and warp of a workpiece) thanpolishing using a polishing pad having a hard polishing layer molded bya dry method, the polishing pad having a soft polishing layer has thefollowing problem. Specifically, because of its anisotropic cell shape,the state of the openings on the surface changes due to wearing, or alow-density portion of the polishing layer at a lower portion thereof istorn off. Hence, the polishing pad having a soft polishing layer cannotretain a polishing state at a certain level for a long period.

Hence, there is a need for a polishing pad which can be used also forfinish polishing, while taking advantages of a polishing pad having apolishing layer molded by a dry method.

The present invention has been made in view of the above-describedproblems, and an object of the present invention is to provide apolishing pad which remedies the problem of scratches occurring when aconventional hard (dry) polishing pad is used, which is excellent inpolishing rate and polishing uniformity, and which can be used for notonly primary polishing but also finish polishing, and a manufacturingmethod therefor.

Means for Solving the Object

To achieve the above object, the present invention employs the followingconfigurations.

1. A polishing pad for polishing a semiconductor device, comprising apolishing layer having a polyurethane-polyurea resin foam containingsubstantially spherical cells, wherein

the polyurethane-polyurea resin foam has a hard segment content (HSC) ina range from 26 to 34%, and

the polyurethane-polyurea resin foam has a density D in a range from0.30 to 0.60 g/cm³,

the hard segment content (HSC) being determined by the following formula(1):

HSC=100×(r−1)×(Mdi+Mda)÷(Mg+r×Mdi+(r−1)×Mda)  (1)

wherein Mdi represents an average molecular weight of a polyisocyanatecompound(s) constituting the polyurethane-polyurea resin per twoisocyanate functional groups; Mg represents an average molecular weightof a polyol compound(s) constituting the polyurethane-polyurea resin pertwo hydroxyl functional groups; Mda represents an average molecularweight of a polyamine compound(s) constituting the polyurethane-polyurearesin per two amino functional groups; and r represents the equivalenceratio of isocyanate groups of the polyisocyanate compound(s)constituting the polyurethane-polyurea resin to hydroxyl groups of thepolyol compound(s) constituting the polyurethane-polyurea rosin.

2. The polishing pad according to 1, wherein

the polyurethane-polyurea resin foam has a Y value in a range from 50 to65, the Y value being determined by Y=HSC+65×D, wherein D represents adensity (g/cm³) and HSC is the value determined by the formula (1).

3. The polishing pad according to 1 or 2, wherein

the polyurethane-polyurea resin foam has an average cell diameter of 120to 185 μm.

4. The polishing pad according to any one of 1 to 3, wherein

the polyurethane-polyurea resin foam has a type A hardness of 20 to 55degrees.

5. The polishing pad according to any one of 1 to 4, wherein

the polyurethane-polyurea resin foam has a type D hardness of 5 to 35degrees.

6. The polishing pad according to any one of 1 to 5, wherein

the polyurethane-polyurea resin foam has a storage elastic modulus E′ of1 to 30 MPa, the storage elastic modulus E′ being measured at 40° C.with an initial load of 10 g, a strain range of 0.01 to 4%, and ameasuring frequency of 0.2 Hz in a tensile mode.

7. The polishing pad according to any one of 1 to 6, wherein

a layer harder than the polishing layer is laminated on a surface of thepolishing layer, the surface being opposite from a polishing surface ofthe polishing layer.

8. A method for manufacturing the polishing pad according to any one of1 to 7, the method comprising:

a preparation step of preparing an isocyanate group-containing compound(A), a polyisocyanate compound (B), a polyamine compound (D), a mixtureliquid (E) comprising water, a foam stabilizer, and a reaction catalyst,and a gas non-reactive with all the components;

a mixing step of mixing at least the isocyanate group-containingcompound (A), the polyisocyanate compound (B), the polyamine compound(D), the mixture liquid (E) comprising the water, the foam stabilizer,and the reaction catalyst, and the gas non-reactive with all thecomponents with each other to obtain a mixture liquid for molding afoam;

a foam-molding step of molding a polyurethane-polyurea resin foam fromthe mixture liquid for molding a foam; and

a polishing layer formation step of forming a polishing layer having apolishing surface for polishing a workpiece from thepolyurethane-polyurea resin foam.

9. The method for manufacturing the polishing pad according to 8,wherein

in the preparation step, a polyol compound (C-2) is further prepared,and

in the mixing step, the polyol compound (C-2) is mixed.

10. The method for manufacturing the polishing pad according to 9,wherein

in the preparation step, the polyamine compound (D) and the polyolcompound (C-2) are prepared, with the equivalence ratio of amino groupsof the polyamine compound (D) to the sum of the chemical equivalents ofamino groups of the polyamine compound (D) and hydroxyl groups of thepolyol compound (C-2) (the chemical equivalent of active hydrogengroups) being 0.70 to 0.97 (the amino groups/(the amino groups+thehydroxyl groups)).

11. The method for manufacturing the polishing pad according to any oneof 8 to 10, wherein the polyamine compound (D) is a crudemethylenebis(o-chloroaniline) (MOCA) which is a mixture of monomer andmultimers of MOCA and which contains the multimers in an amount of 15%by mass or more.12. The method for manufacturing the polishing pad according to 9 or 10,wherein the polyol compound (C-2) is poly(tetramethylene glycol) orpoly(propylene glycol) having a number average molecular weight of 500to 5000, or a mixture thereof.

Advantageous Effects of Invention

Since the polishing pad of the present invention has a low hard segmentcontent (HSC), the strong pressing to a workpiece is suppressed, andscars (scratches) are less likely to be formed. In addition, because ofthe high porosity (low density), scars due to clogging are also lesslikely to be formed. Moreover, since the polishing pad of the presentinvention is softer than polishing pads having polishing layers moldedby conventional dry methods, the polishing pad of the present inventionis excellent also in polishing rate and polishing uniformity. Meanwhile,since the polishing pad of the present invention is dry-molded, thepolishing pad of the present invention has a lower wearing rate of thepolishing surface and undergoes less change in cell diameters in thedepth direction than the wet-molded polishing pads. Hence, the polishingpad of the present invention can retain a constant polishing state for along period. Therefore, although dry-molded, the polishing pad of thepresent invention can be advantageously used for both primary processingand finish processing.

BRIEF DESCRIPTION OF DRAWINGS Brief Explanation of Drawings

FIG. 1 shows a cross-sectional view (left) of a polishing pad showing anembodiment of the present invention and a cross-sectional view (right)of a polishing pad (Comparative Example 1) having a polishing layerdry-molded by a conventional technique.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for carrying out the present invention aredescribed.

<<Polishing Pad>>

The polishing pad of the present invention comprises a polishing layerhaving a polyurethane-polyurea resin foam containing substantiallyspherical cells, and is characterized in that the polyurethane-polyurearesin foam has a hard segment content (IISC) in a range from 26 to 34%,and has a density D in a range from 0.30 to 0.60 g/cm³.

HSC=100×(r−1)×(Mdi+Mda)÷(Mg+r×Mdi+(r−1)×Mda)  (1)

where Mdi represents an average molecular weight of a polyisocyanatecompound(s) constituting the polyurethane-polyurea resin per twoisocyanate functional groups; Mg represents an average molecular weightof a polyol compound(s) constituting the polyurethane-polyurea resin pertwo hydroxyl functional groups; Mda represents an average molecularweight of a polyamine compound(s) constituting the polyurethane-polyurearesin per two amino functional groups; and r represents the equivalenceratio of isocyanate groups of the polyisocyanate compound(s)constituting the polyurethane-polyurea resin to hydroxyl groups of thepolyol compound(s) constituting the polyurethane-polyurea resin.

The polyurethane-polyurea resin foam means a resin foam having at leasttwo urethane bonds or more and at least two urea bonds or more in itsmolecule. The polyurethane-polyurea resin foam of the present inventioncan be manufactured from an isocyanate group-containing compound formedby reacting a polyisocyanate compound with a polyol compound, apolyisocyanate compound, a polyamine compound, and a mixture liquidcomprising water, a foam stabilizer, and a reaction catalyst(hereinafter, abbreviated as an aqueous dispersion in some cases).

In addition, the substantially spherical is a concept meaning anordinary shape of cells (a shape which is isotropic, and is spherical,elliptical, or close to any of these shapes) present in a foam molded bya dry method (see FIG. 1). These cells are clearly distinguished fromcells contained in a foam molded by a wet method (which are anisotropic,and have a structure in which the diameter increases from a polishinglayer surface of a polishing pad to a bottom portion thereof).

(Hard Segment Content (HSC))

The hard segment content (HSC) (%) is a value determined by theabove-described formula (1).

In general, a polyurethane-polyurea resin is a block copolymerconstituted of soft segments of a prepolymer formed by a reaction of apolyisocyanate compound with a polyol compound, and hard segments (ureasegments) formed by adding a polyamine compound to the prepolymer afterformation, and allowing a reaction between the polyisocyanate compoundin excess with the polyamine compound (in the present invention, theurethane bonds of the polyurethane-polyurea resin are regarded as thesoft segments).

In the hard segments, urea bonds are present between the polyisocyanatecompound and the polyamine compound. The urea bonds form strongerhydrogen bonding than urethane bonds. Hence, when the urea bonds arepresent in a larger amount, a harder crystal layer is formed, because ofaggregation occurring between multiple hard segments due to the hydrogenbonding. In addition, as the urea bonds become closer to each other(regular polyurea segment), a stronger cohesive force is exerted betweenthe hard segments of adjacent molecules, and a more rigid crystal layeris formed.

On the other hand, when the ratio of the soft segments is high (i.e.,the ratio of the polyol compound is high), the mobility increases, andthe resin becomes soft. Hence, the hardness of the polishing layer canbe adjusted based on the HSC value (for the calculation formula (I) ofthe HSC, see, for example, P. J. Flory; Journal of American ChemicalSociety, 58, 1877-1885 (1936)).

Note that the HSC can be calculated from Mdi, Mg, Mda, and r, which aredetermined by structural analysis of the polyurethane-polyurea resinconstituting the polishing layer based on a nuclear magnetic resonance(NMR) spectrum, or the like. Thus, the HSC of the polyurethane-polyurearesin constituting the polishing layer can be determined also for thepolishing pad after molding.

In Description and Claims, the hard segment content (HSC) is 26 to 34%,and particularly preferably 27 to 32%. When the hard segment content(HSC) is within this range, the shape of the polishing pad can bemaintained moderately because of the urea bonds, and elasticity can alsobe obtained. Hence, the strong pressing against a workpiece is reduced,so that scars (scratches) are less likely to be formed. In addition,polishing can be achieved at a high polishing rate, without impairingthe polishing flatness.

(Density D)

The density D of the polyurethane-polyurea resin foam is 0.30 to 0.60g/cm³, more preferably 0.35 to 0.55 g/cm³, and further more preferably0.35 to 0.50 g/cm³. When the density D is within the range, thepossibility of the formation of scars due to the clogging of thepolishing layer surface with a polishing agent or dust from a workpieceor the like is reduced. In contrast, if the density D is lower than thelower limit value, the planarization performances deteriorate, becausethe elasticity is excessively high, and hence the pad itself greatlydeforms upon contact with a workpiece. On the other hand, if the densityD is higher than the upper limit value, scratches are formed because ofthe lack of elasticity.

In particular, since both the hard segment content (HSC) and the densityD are restricted within the above-described numeric value ranges,respectively, in the present invention, it is possible to obtain apolishing pad excellent in terms of all the scratch reduction, thepolishing rate, and the polishing uniformity.

In addition to the above, the Y value of the polyurethane-polyurea resinfoam calculated by Y=HSC+65×D is preferably in a range from 50 to 65,more preferably from 51 to 64, and further more preferably from 53 to60, where D represents a density (g/cm³), and the HSC is the valuedetermined by the formula (1).

Here, the significance of the Y value is that the HSC and the density,each of which is a factor determining characteristics such as the scars,the rate, and the flatness, have the optimum values not in anindependent manner but in an interactive manner. As a result ofintensive studies, it has been found that, when the Y value is withinthe above-described range, the scratch reduction, the polishing rate,and the polishing uniformity can be achieved, while a certain flatnessis retained.

Although it is not clear why the above-described effects can be achievedwhen the Y value is within the above-described range, we presume thatthe surface of the polishing layer becomes softer during the use of thepolishing pad, while the inside of the polishing layer is kept hard.

(Average Cell Diameter d)

In Description and Claims, the average cell diameter is an averagevalues of equivalent circle diameters calculated from the areas of cellportions and the number of the cell portions obtained by binarization ofan surface image of the polishing pad (note that this average values isa numeric value obtained in the case where the “cutoff value” forcutting noises is set to 10 μm in the image processing).

The average cell diameter d (μm) of the polyurethane-polyurea resin foamof the polishing layer is preferably 120 to 185 μm, and more preferably140 to 170 μm. If the average cell diameter (μm) is higher than theupper limit value, the polishing layer surface is so rough that apolishing quality of a workpiece deteriorates. If the average celldiameter (μm) is lower than the lower limit value, scratches tend to beformed, because of clogging of the polishing layer surface or loss offlexibility of the polishing layer surface.

(Type A Hardness and Type D Hardness)

In Description and Claims, the type A hardness means a value measuredaccording to JIS K 7311.

Meanwhile, the type D hardness means a value measured according to JIS K6253-1997/ISO 7619.

In addition, the type A hardness of the polyurethane-polyurea resin foamis preferably 20 to 55 degrees.

Meanwhile, the type D hardness of the polyurethane-polyurea resin foamis preferably 5 to 35 degrees.

If the type A hardness and/or the type D hardness is/are below theabove-described range(s), the elasticity is excessively high, and hencethe pad itself greatly deforms upon contact with a workpiece, resultingin a poor planarization performance. Meanwhile, if the type A hardnessand/or the type D hardness exceed(s) the above-described range(s),scratches are formed, because of the lack of elasticity.

(Storage Elastic Modulus E′)

In Description and Claims, the storage elastic modulus E′ is measuredaccording to JIS K 7244-4 with an initial load of 10 g, a strain rangeof 0.01 to 4%, and a measuring frequency of 0.2 Hz at 40° C.

The storage elastic modulus E′ of the polyurethane-polyurea resin foammeasured at 40° C. with an initial load of 10 g, a strain range of 0.01to 4%, and a measuring frequency of 0.2 Hz in a tensile mode ispreferably 1 to 30 MPa, more preferably 1 to 25 MPa, and furtherpreferably 1 to 20 MPa. If the storage elastic modulus E′ is below theabove-described range, the pad itself tend to deform due to offset loadtemporarily applied during the polishing, which results in a poorpolishing uniformity. Meanwhile, if the storage elastic modulus E′ islarger than the above-described range, scratches tend to be formed,because of the lack of elasticity.

The polishing pad of the present invention can be suitably used forpolishing a semiconductor device, and especially for chemical mechanicalpolishing (CMP) of a semiconductor device.

<<Method for Manufacturing Polishing Pad>>

A method for manufacturing a polishing pad for polishing a semiconductor device of the present invention by which the above-describedpolishing pad for polishing a semiconductor device of the presentinvention can be manufactured comprises: a preparation step of preparingan isocyanate group-containing compound (A), a polyisocyanate compound(B), a polyamine compound (D), an aqueous dispersion (a mixture liquidcomprising water, a foam stabilizer, and a reaction catalyst) (E), and agas non-reactive with all the components; a mixing step of mixing atleast the isocyanate group-containing compound (A), the polyisocyanatecompound (B), the polyamine compound (D), the aqueous dispersion (E),and the gas non-reactive with all the components with each other toobtain a mixture liquid for molding a foam; a foam-molding step ofmolding a polyurethane-polyurea resin foam from the mixture liquid formolding a foam; and a polishing layer formation step of forming apolishing layer having a polishing surface for polishing a workpiecefrom the polyurethane-polyurea resin foam.

Hereinafter, the preparation step, the mixing step, the foam-moldingstep, and the polishing layer formation step are described separately.

<Preparation Step>

For manufacturing the polishing pad of the present invention, at leastan isocyanate group-containing compound (A), a polyisocyanate compound(B), a polyamine compound (D), an aqueous dispersion (E), and a gasnon-reactive with all of these components are used as raw materials ofthe polyurethane-polyurea resin foam. Moreover, a polyol compound may beused with the above-described components.

In addition, as long as the effects of the present invention are notimpaired, components other than those described above may be used incombination.

Hereinafter, each of the components is described.

[(A) Isocyanate Group-Containing Compound]

The isocyanate group-containing compound, which is a prepolymer, isobtained by reacting the following polyisocyanate compound and polyolcompound under ordinary conditions. In addition, other components may becontained in the isocyanate group-containing compound, as long as theeffects of the present invention are not impaired.

As the isocyanate group-containing compound, a commercially availablecompound may be used, or a compound synthesized by reacting apolyisocyanate compound with a polyol compound may be used. The reactionis not particularly limited, and it is only necessary to carry out anaddition polymerization reaction by employing a known method andconditions for manufacturing a polyurethane resin. For example, theisocyanate group-containing compound can be manufactured by a method inwhich a polyisocyanate compound heated to 50° C. is added to a polyolcompound heated to 40° C. with stirring in a nitrogen atmosphere, thetemperature is raised to 80° C. in 30 minutes, and the reaction isallowed to further proceed at 80° C. for 60 minutes.

In addition, when the polyisocyanate compound is added in excess of thepolyol compound for manufacturing the isocyanate group-containingcompound (A), the polyisocyanate compound remains in the reactionsolution even after the formation of the isocyanate group-containingcompound. Hence, the reaction solution can also be used in thesubsequent mixing step, without additionally preparing thepolyisocyanate compound in the preparation step.

[(B) Polyisocyanate Compound]

In Description and Claims, the polyisocyanate compound means a compoundhaving two or more isocyanate groups in its molecule.

The polyisocyanate compound is not particularly limited, as long as ithas two or more isocyanate groups in its molecule. Examples ofdiisocyanate compounds having two isocyanate groups in its moleculeinclude m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylenediisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2,4-TDI),naphthalene-1,4-diisocyanate, diphenylmethane-4,4′-diisocyanate (MDI),4,4′-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI),3,3′-dimethoxy-4,4′-biphenyl diisocyanate,3,3′-dimethyldiphenylmethane-4,4′-diisocyanate,xylylene-1,4-diisocyanate, 4,4′-diphenylpropane diisocyanate,trimethylene diisocyanate, hexamethylene diisocyanate,propylene-1,2-diisocyanate, butylene-1,2-diisocyanate,cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate,p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, ethylidynediisothiocyanate, and the like.

The polyisocyanate compound is preferably a diisocyanate compound, and,among diisocyanate compounds, 2,4-TDI and MDI are more preferable, and2,4-TDI is particularly preferable.

One of these polyisocyanate compounds may be used alone, or multiplepolyisocyanate compounds may be used in combination.

[(C) Polyol Compound]

In Description and Claims, the polyol compound means a compound havingtwo or more alcoholic hydroxyl groups (OH) in its molecule.

((C-1) Polyol Compound for Prepolymer Synthesis)

The polyol compound used for synthesizing the Isocyanategroup-containing compound, which is a prepolymer, includes diolcompounds, triol compounds, and the like such as ethylene glycol andbutylene glycol; polyether polyol compounds such as poly(tetramethyleneglycol) (PTMG); polyester polyol compounds such as a reaction product ofethylene glycol with adipic acid and a reaction product of butyleneglycol with adipic acid; polycarbonate polyol compounds;polycaprolactone polyol compounds; and the like. Of these compounds,PTMG is preferable, and PTMG having a number average molecular weight(Mn) of approximately 500 to 5000 is further more preferable, and PTMGhaving a number average molecular weight (Mn) of approximately 1000 ismost preferable.

One of the above-described polyol compounds may be used alone, ormultiple polyol compounds may be used in combination.

In addition, the NCO equivalent weight of the prepolymer, which can bedetermined by “(the mass (parts) of the polyisocyanate compound+the mass(parts) of the polyol compound (C-1))/[(the number of functional groupsper molecule of the polyisocyanate compound×the mass (parts) of thepolyisocyanate compound/the molecular weight of the polyisocyanatecompound)−(the number of functional groups per molecule of the polyolcompound (C-1)×the mass (parts) of the polyol compound (C-1)/themolecular weight of the polyol compound (C-1))]” is a numeric valuerepresenting the molecular weight of the PP (prepolymer) per NCO group,and can be used as an index for estimating the ratio of “the softsegments/the hard segments.” The NCO equivalent weight is preferably 400to 650.

((C-2) Polyol Compound which May be Used after Prepolymer Synthesis)

In addition, in the present invention, besides the polyol compound usedfor forming the isocyanate group-containing compound, which is theprepolymer, a polyol compound can also be added into a mixer and mixedwith the isocyanate group-containing compound, the polyisocyanatecompound, the polyamine compound, and the like. The polyol compound maybe prepared by itself, or prepared as a mixture liquid with thepolyamine compound, or added during the preparation of the aqueousdispersion. The polyol compound acts as a curing agent for curing theprepolymer. The polyol compound is incorporated by a competitivereaction with the polyamine compound. Thus, the polyol compound inhibitsuneven chain elongation reaction of the polyamine compound among theblocks, and makes it easier to carry out the polymerization with lessuneven degrees of polymerization.

As the polyol compound, compounds such as diol compounds and triolcompounds can be used without any particularly limitation. In addition,the polyol compound may be the same as or different from the polyolcompound used for forming the prepolymer.

Specific examples thereof include low-molecular weight polydiols such asethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol,1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol,pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol; highmolecular weight polyol compounds such as poly(tetramethylene glycol),polyethylene glycol, and poly (propylene glycol); and the like. Of thesepolyols, two-functional or three-functional poly(propylene glycol) (PPG)(here, three-functional poly(propylene glycol) means poly(propyleneglycol) having a branch obtained by using, as a polymerizationinitiator, glycerin having multiple functional groups) andpoly(tetramethylene glycol) are preferable from the viewpoints of thecompatibility with the other components in the mixing step and theuniformity of the obtained cells. Poly(propylene glycol) and/orpoly(tetramethylene glycol) having a number average molecular weight(Mn) of approximately 500 to 5000 are/is more preferable, poly(propyleneglycol) having an Mn of approximately 2000 to 4000 and/or poly(tetramethylene glycol) having an Mn of approximately 500 to 1500 are/isfurther preferable, and poly(propylene glycol) having a Mn ofapproximately 3000 and/or poly(tetramethylene glycol) having an Mn ofapproximately 1000 are/is most preferable. In addition, thepoly(propylene glycol) is preferably three-functional poly(propyleneglycol).

One of the polyol compounds (C-2) may be used alone, or multiple polyolcompounds (C-2) may be used in combination.

When the polyol compound (0-2) is used, the polyol compound (0-2) ispreferably prepared, with the equivalence ratio (hereinafter, referredto also as an s value) of the amino groups of the polyamine compound tothe sum of the chemical equivalents of the amino groups of the polyaminecompound described later and the hydroxyl groups of the polyol compoundprepared separately from the isocyanate group-containing compound (thechemical equivalent of active hydrogen groups) being 0.70 to 0.97 (theamino groups/(the amino groups+the hydroxyl groups)).

One of the polyol compounds may be used alone, or multiple polyolcompounds may be used in combination.

[(D) Polyamine Compound]

In Description and Claims, the polyamine compound means a compoundhaving two or more amino groups in its molecule.

The polyamine compound acts as a chain extender. Part of the polyaminecompound reacts with the polyisocyanate compound to form hard segments,and other part of the polyamine compound is bonded to terminals of mainchains of the isocyanate group-containing compound (soft segmentportions), so that the polymer chains can be further extended. Thus, apolyurethane-polyurea resin having a block copolymer of hard segmentsand soft segments is formed.

As the polyamine compound, an aliphatic or aromatic polyamine compound,and especially a diamine compound can be used. Examples of the polyaminecompound include ethylenediamine, propylenediamine,hexamethylenediamine, isophoronediamine,dicyclohexylmethane-4,4′-diamine,3,3′-dichloro-4,4′-diaminodiphenylmethane (methylenebis(o-chloroaniline)) (hereinafter, abbreviated as MOCA), polyaminecompounds having structures similar to that of MOCA, and the like. Inaddition, the polyamine compound may have a hydroxyl group, and examplesof such an amine-based compound include 2-hydroxyethylethylenediamine,2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine,di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine,di-2-hydroxypropylethylenediamine, and the like.

The polyamine compound is preferably a diamine compound, more preferablyMOCA, diaminodiphenylmethane, or diaminodiphenyl sulfone, andparticularly preferably MOCA.

Here, solid MOCA and crude MOCA are known as the MOCA. The solid MOCAmeans pure MOCA, which is solid at room temperature. The crude MOCA is amixture of monomer of MOCA and multimers of MOCA, and a crude MOCA inwhich the ratio of the multimers is 15% by mass or higher is preferablyused. The ratio of the multimers is more preferably 10 to 50% by mass,and further more preferably 20 to 40% by mass. Examples of the multimersinclude dimer, trimer, and tetramer of MOCA, and the like. The crudeMOCA makes it easier to control the reaction rate, and consequentlymakes it easier to obtain physical properties (for example, density,hardness, and the like) uniform all over the foam.

“Solid MOCA” and “crude MOCA” used in Description and Claims mean theabove-described solid MOCA and the above-described crude MOCA,respectively.

One of the polyamine compounds may be used alone, or multiple polyaminecompounds may be used in combination. In addition, since the solid MOCAand the crude MOCA are solid at normal temperature, the solid MOCA andthe crude MOCA have to be used in a molten state in the mixing step byheating at about 120° C. In this respect, when the polyol compound (C-2)is used, it is preferable to use the MOCA, particularly the crude MOCA,dissolved in the polyol compound (C-2) in advance, because the MOCA canbe used in the mixing step without heating to the melting temperature,and uneven polymerization due to the increase in reactivity by theheating can be suppressed. When the MOCA is used by being dissolved asdescribed above, the mass ratio of the MOCA to the polyol compound (C-2)is preferably 3:1 to 1:3, more preferably 2:1 to 1:2, and particularlypreferably 1:1. Moreover, the polyol compound (C-2) in which the MOCA isdissolved is preferably poly(tetramethylene glycol), more preferablypoly(tetramethylene glycol) having a number average molecular weight(Mn) of approximately 500 to 5000, further preferablypoly(tetramethylene glycol) having an Mn of approximately 500 to 1500,and most preferably poly(tetramethylene glycol) having an Mn ofapproximately 1000.

In order to facilitate the mixing of the polyamine compound with theother components and/or improve the uniformity of the cell diameters inthe subsequent foam-molding step, the polyamine compound is preferablydegassed under reduced pressure, if necessary, in a heated state. As thedegassing method under reduced pressure, a method known formanufacturing a polyurethane-polyurea may be used. For example, thepolyamine compound can be degassed by using a vacuum pump at a degree ofvacuum of 0.1 MPa or less.

When a solid compound is used as the chain extender, the compound can bedegassed under reduced pressure, while being melt by heating.

On the other hand, when a polyamine compound which is liquid at roomtemperature is used, the polyamine compound may be degassed underreduced pressure without heating.

In the method for manufacturing a polishing pad of the presentinvention, the content ratio (molar ratio or equivalence ratio) of thepolyamine compound to the polyol compound used for forming theprepolymer and/or all the polyol compounds is extremely smaller than thecontent ratios employed in conventional manufacturing of polishing pads.

Specifically, the HSCs of conventional polishing pads are 35% or higher,whereas the HSC of the present invention is 26 to 34%, and preferably 27to 32%.

In addition, when the solid MOCA is used as the polyamine compound, thesolid MOCA is preferably used in an amount of 150 to 205 parts by massrelative to 1000 parts by mass which is the total of the polyisocyanatecompound and the polyol compound (C-1). When a liquid MOCA (detailsthereof are described later) is used as the polyamine compound, theliquid MOCA is preferably used in an amount of 200 to 400 parts by massrelative to 1000 parts by mass which is the total of the polyisocyanatecompound and the polyol compound (C-1).

[(E) Aqueous Dispersion]

In Description and Claims, the aqueous dispersion means a mixture liquidcomprising water, a foam stabilizer, and a reaction catalyst.

The aqueous dispersion contributes as a blowing agent and a catalyst foraddition polymerization and to foam stabilization associated with foamdiameters and foam uniformity. For example, the aqueous dispersion canbe prepared by stirring and mixing water, a reaction catalyst, asurfactant, and the like by using an ordinary stirrer. Of course, theaqueous dispersion is not limited to only those consisting of thecombination of these three components.

Water contained in the aqueous dispersion is preferably distilled waterfrom the viewpoint of preventing contamination with impurities. Thewater is used at a ratio of preferably 0.1 to 6 parts by mass, morepreferably 0.5 to 5 parts by mass, and further more preferably 1 to 3parts by mass, relative to 1000 parts by mass of the prepolymer.

As the reaction catalyst (hereinafter, sometimes simply referred to alsoas a catalyst) contained in the aqueous dispersion, a known reactioncatalyst can be used. Examples of the catalyst include amine catalystssuch as tertiary amines, alcohol-amines, and ether-amines (for example,TOYOCAT-ET); acetates (of potassium or calcium), organometalliccatalysts, and the like. Note that, in Examples,bis(2-dimethylaminoethyl)ether (TOYOCAT-ET manufactured by TosohCorporation) was used as the catalyst. However, the effects of thepresent invention are not limited to cases where this catalyst is used.The amount of the catalyst is not particularly limited, and is used at aratio of preferably 0.01 to 5 parts by mass, and more preferably 0.5 to3 parts by mass, relative to 1000 parts by mass of the prepolymer.

As the surfactant serving as a foam stabilizer and contained in theaqueous dispersion, a known surfactant can be used. Examples of thesurfactant include polyether-modified silicones and the like. Note that,in Examples, SH-193 (manufactured by Dow Corning Corporation), which isone of the silicone-based surfactants, was used. However, the effects ofthe present invention are not limited to cases where this surfactant isused. The amount of the surfactant is not particularly limited, and ispreferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 partsby mass, relative to 1000 parts by mass of the prepolymer.

Moreover, in addition to the above-described components, known flameretardant, coloring agent, plasticizer, and the like may be contained inthe aqueous dispersion, as long as the effects of the present inventionare not impaired.

<Mixing Step>

In the mixing step, the isocyanate group-containing compound(prepolymer) (A), the polyisocyanate compound (B), the polyaminecompound (D), and the aqueous dispersion (E) obtained in the preparationstep and The prepolymer formation step are supplied to a mixer. Here,the gas non-reactive with all the components is introduced into thecomponents. The supplied non-reactive gas is stirred and mixed with theabove-described components in the mixer, so that a mixture liquid formolding a foam in which bubbles are formed is prepared. The mixing stepis conducted with heating to a temperature at which the above-describedcomponents can retain their flowability.

For example, solid MOCA (120° C.) or MOCA (80° C.) dissolved in thepolyol compound (C-2) and a dispersion containing the catalyst, and thelike may be added to a prepolymer (isocyanate) solution heated to 30° C.to 100° C. in a mixer equipped with a jacket capable of temperatureadjustment, and the mixture liquid may be stirred at 80° C. Ifnecessary, the mixture liquid may be transferred to a tank equipped withan agitator and a jacket, and aged. The stirring time is adjusted, asappropriate, depending on the number of the blades, the number ofrevolutions, the clearance, and the like of the mixer, and is, forexample, 0.5 to 600 seconds.

As the gas, any gas non-reactive with all the above-described componentscan be used without limitation. For example, air, nitrogen, oxygen,carbon dioxide, helium, argon, and the like can be used.

Regarding the amount of the gas supplied, the supply rate and the supplytime are adjusted, so that the amount of the gas supplied can be in arange of preferably 0.10 to 4.00 L, and more preferably 0.17 to 3.33 Lper kilogram of the total amount of the above-described components.

<Foam-Molding Step>

In the foam-molding step, a polyurethane-polyurea resin foam is moldedby pouring the mixture liquid for molding a foam prepared in the mixingstep into a mold heated at 50 to 100′C to thereby foam and cure themixture liquid. Here, the prepolymer, the polyisocyanate compound, andthe polyamine compound (and the polyol compound) react with each otherto form the polyurethane-polyurea resin, and thus the mixture liquid iscured. Here, water contained in the aqueous dispersion reacts withisocyanate groups in the prepolymer to generate carbon dioxide. Thegenerated carbon dioxide and the introduced gas remain in thepolyurethane-polyurea resin, so that a polyurethane-polyurea resin foamas shown in FIG. 1 having many substantially spherical and fine cells isformed.

Note that, in FIG. 1, the photographs of a cross-sectional view (left)of a polishing pad showing an embodiment of the present invention and across-sectional view (right) of a polishing pad (Comparative Example 1)having a polishing layer dry-molded by a conventional technique weretaken at the same magnification (×100), and the white bar in the rightphotograph represents a length of 100 μm.

<Polishing Layer Formation Step>

The polyurethane-polyurea resin foam obtained in the foam-molding stepis sliced into a sheet shape. Thus, a polyurethane-polyurea sheet isformed. By this slicing, openings are formed on the sheet surface. Here,to form openings excellent in wear resistance and resistant to cloggingon the polishing layer surface, it is preferable to conduct aging at 30to 80° C. for about 1 hour to 2 weeks. The aging makes it easier toobtain desired elasticity characteristics. Here, the average celldiameter in the foam is preferably set within the above-described range,i.e., 120 to 185 μm, and further preferably 140 to 170 μm. The averagecell diameter can be adjusted within the above-described range bycontrolling the temperature (viscosity) of the prepolymer, the number ofrevolutions of the stirring, the air flow rate, the type and theconcentration of the foam stabilizer, and the mold temperature.

Then, after a double-sided tape is attached onto a surface of the thusobtained polishing layer having a polyurethane-polyurea sheet, thesurface being opposite from the polishing surface of the polishinglayer, the polishing layer is cut into a given shape, preferably a diskshape, and completed as a polishing pad of the present invention. Thedouble-sided tape is not particularly limited, and any double-sided tapeselected from double-sided tapes known in this technical field can beused.

In addition, the polishing pad of the present invention may have asingle-layer structure consisting only of the polishing layer, or may becomposed of multiple layers by laminating another layer (underlininglayer, supporting layer) on the surface of the polishing layer oppositefrom the polishing surface. The characteristics of said another layerare not particularly limited, and it is preferable to laminate a layerharder (having a higher type A hardness and/or a higher type D hardness)than the polishing layer on the surface opposite from the polishinglayer. By providing the layer harder than the polishing layer, theinfluence of fine asperity on the polishing platen on the shape of thepolishing surface can be avoided, so that the polishing flatness isfurther improved. Moreover, the rigidity of the polishing cloth isgenerally increased, so that the formation of wrinkles and the like canbe prevented at the time of attachment of the polishing cloth onto theplaten.

When the polishing pad of the present invention has a multi-layerstructure, the multiple layers may be adhered and fixed to each other byusing a double-sided tape or an adhesive agent, if necessary, underpressure. The double-sided tape or the adhesive agent used here is notparticularly limited, and any double-sided tape or adhesive agentselected from those known in this technical field can be used.

Moreover, if necessary, the polishing pad of the present invention maybe subjected to a grinding treatment on the front surface and/or theback surface of the polishing layer, or grooving or embossing on thefront surface. Moreover, a substrate and/or an adhesive layer may belaminated on the polishing layer, and the polishing layer may include alight-transmission portion.

The grinding method is not particularly limited, and the grinding can beconducted by a known method. Specifically, the grinding may be conductedby using sandpaper.

The pattern achieved by the grooving or embossing is not particularlylimited, and examples of the pattern include a lattice pattern, aconcentric-circular pattern, a radial pattern, and the like.

When the polishing pad of the present invention is used, the polishingpad is attached to a polishing platen of a polishing machine, with thepolishing surface of the polishing layer facing a workpiece. Then, whilea polishing agent slurry is supplied, the polishing platen is rotated.Thus, the work surface of the workpiece is polished.

The workpiece to be processed by the polishing pad of the presentinvention may be a glass substrate for a hard disk, mother glass for athin display, a semiconductor wafer, a semiconductor device, or thelike. Especially, the polishing pad of the present invention is suitablyused for processing a semiconductor device.

<<Operations and Effects>>

The CMP polishing pad of the present invention has the polishing layercontaining the polyurethane-polyurea resin foam, the hard segmentcontent (HSC) of the polyurethane-polyurea resin foam is 26 to 34%, andthe density D of the polishing layer is set within the range from 0.30to 0.60 g/cm³.

The polishing layer made of the polyurethane-polyurea resin andsatisfying the above-described ranges has a lower hard segment contentand a lower density than hard polyurethane polishing layers molded by aconventional dry method. Hence, a polishing pad having a lower hardnessthan conventional ones can be obtained. Accordingly, the strong pressingof the polishing layer to a workpiece is prevented, so that scratchesare less likely to be formed on the surface of the workpiece. Inaddition, the polishing rate and the polishing uniformity are alsoimproved. Furthermore, since the polishing layer has a low density,scratches due to clogging with the slurry, polishing dust, or the likeare also less likely to be formed.

On the other hand, in the polishing pad of the present invention,openings having the shapes obtained by slicing the substantiallyspherical cells are provided, and the polishing pad of the presentinvention has an isotropic cell structure uniform in the thicknessdirection and the plane direction of the polishing layer. Hence, thepolishing pad of the present invention has a different pore (opening)shape on the polishing layer surface from that of a polishing pad(abbreviated as a soft (wet) polishing pad) molded by a conventional wetmethod and having an anisotropic foam structure having relatively largeopening portions of a suede type. A soft (wet) polishing pad has astructure in which the cell diameter gradually increases from thepolishing surface to the bottom portion. Hence, the soft (wet) polishingpad has a problem that, as the polishing pad wears with polishing, thecell diameter (the diameters of the openings) on the surface increases,and the surface becomes rough, so that the polishing qualitydeteriorates. In addition, since the cells become larger to the bottomportion in this structure, the soft (wet) polishing pad has a problemthat the surface is worn by tearing off due to the polishing resistance.In contrast, since the polishing pad of this invention is molded by adry method, the cells are isotropic. Hence, the polishing pad of thisinvention achieves an effect of reducing the occurrence of theabove-described problems observed in the wet polishing pad.

As described above, since the polishing pad of the present invention issofter and smaller in density than conventional hard (dry) polishingpad, the occurrence of scratches can be reduced, and the polishing padis excellent in polishing rate and polishing uniformity. Hence, thepolishing pad of the present invention can be used not only for primaryprocessing, but also for finish processing. Moreover, when the Y valueis limited to the certain range, the polishing rate and the polishinguniformity can be further improved, while the planarization performanceis maintained to same degree.

EXAMPLES

Hereinafter, the present invention will be described in further detailbased on examples. However, the present invention is not limited tothese examples.

In each of Examples and Comparative Example, as well as Tables 1 to 4,“parts” means “parts by mass,” unless otherwise noted.

In addition, the abbreviations in Tables 1 to 4 have the followingmeanings.

2,4-TDI: 2,4-tolylene diisocyanate

Hydrogenated MDI: 4,4′-methylene-bis(cyclohexyl isocyanate)

PTMG 1000: poly(tetramethylene glycol) having a number average molecularweight of approximately 1000

DEG: diethylene glycol

MOCA: 3,3′-dichloro-4,4′-diaminodiphenylmethane

Three-functional PPG 3000: three-functional poly(propylene glycol)having a number average molecular weight of 3000

In addition, the NCO equivalent weight of a PP (prepolymer) is a numericvalue representing the molecular weight of the PP per NCO group, and isdetermined by “(the mass (parts) of the polyisocyanate compound+the mass(parts) of the polyol compound (C-1))/[(the number of functional groupsper molecule of the polyisocyanate compound×the mass (parts) of thepolyisocyanate compound/the molecular weight of the polyisocyanatecompound)−(the number of functional groups per molecule of the polyolcompound (C-1)×the mass (parts) of the polyol compound (C-1)/themolecular weight of the polyol compound (C-1))].” This NCO equivalentweight was used as an index for estimating the ratio of “the softsegments/the hard segments.”

The s value is, as described above, a numeric value representing theequivalence ratio (amino groups/(amino groups+hydroxyl groups)) of theamino groups of the polyamine compound (D) to the sum (the chemicalequivalent of active hydrogen groups) of the chemical equivalents of theamino groups of the polyamine compound (D) and the hydroxyl groups ofthe polyol compound (C-2) prepared separately from the isocyanategroup-containing compound (A).

Note that the crude MOCA used in the following Examples and ComparativeExamples was a liquid mixture (hereinafter, referred to as a liquidMOCA) of PTMG 1000 and a crude MOCA (multimer content: 40% by mass) at amass ratio of 1:1.

Comparative Example 1

In Comparative Example 1, a conventionally known hard (dry) polishingpad was manufactured. As a first component, which was a prepolymer, anisocyanate group-containing urethane prepolymer having an isocyanatecontent of 9.0% and an NCO equivalent weight of 466 was used. Thisprepolymer was obtained by reacting 316 parts of 2,4-TDI, 88 parts ofhydrogenated MDI, and 539 parts of the PTMG having a number averagemolecular weight of approximately 1000, then adding 57 parts ofdiethylene glycol thereto, and allowing the reaction to further proceed.This prepolymer was heated to 55° C., and degassed under reducedpressure. As a second component, which was a chain extender, a solidMOCA was melted at 120° C., and degassed under reduced pressure. As athird component, a blowing agent (Expancel 551 DE) was mixed with thefirst component at 2% by weight, and the first component and the secondcomponent were supplied to a mixer at a weight ratio of 1000 parts:256parts.

The obtained mixture liquid was poured into a 890×890-mm mold heated to50° C., and cured by heating at 100° C. for 5 hours. Then, the formedpolyurethane resin foam was taken out of the mold. Moreover, this foamwas sliced into sheets having a thickness of 1.25 mm. Thus, urethanesheets were fabricated, and polishing pads were obtained.

Examples 1 to 4 and Comparative Examples 2 to 5

Next, various polishing pads having different densities weremanufactured by using solid MOCA and changing the ratio of components asshown in Table 1.

Example 1

In Example 1, as a first component, which was a prepolymer, anisocyanate group-containing urethane prepolymer having an isocyanatecontent: of 7.8% and an NCO equivalent weight of 540 was used. Theprepolymer was obtained by reacting 2,4-TDI (286 parts) and the PTMG(714 parts) having a number average molecular weight of approximately1000. This prepolymer was heated to 55° C., and degassed under reducedpressure. As a second component, which was a chain extender, solid MOCAwas used. The solid MOCA was melt at 120° C., and degassed under reducedpressure. A third component, an aqueous dispersion, was obtained bymixing the three-functional PPG (42 parts) having a number averagemolecular weight of 3000, water (3 parts), a catalyst (TOYOCAT-ETmanufactured by Tosoh Corporation) (1 part), a silicone-based surfactant(SH-193 manufactured by Dow Corning Corporation) (1 part) with eachother at 35° C. for 1 hour with stirring. Then, the aqueous dispersionwas degassed under reduced pressure. The first component, the secondcomponent, and the third component were supplied to a mixer at a weightratio of 1000 parts:168 parts:47 parts and at a flow rate of 80 kg/min.Here, air was supplied at a flow rate of 18.2 L/min through nozzlesprovided to a stirring rotor of the mixer (specifically, 18.2 L of airwas supplied per 80 kg of the total of the first to third components).The obtained mixture liquid was poured into a mold (890×890 mm) andcured at 100° C. for 5 hours. Then, the formed polyurethane resin foamwas taken out of the mold. This foam was sliced into sheets having athickness of 1.35 ram. Thus, urethane sheets were fabricated, andpolishing pads were obtained.

Examples 2 to 4 and Comparative Examples 2 to 5

Polishing pads having thicknesses of 1.32 to 1.35 mm were obtained bythe same method as in Example 1, except that the ratio of componentssupplied into the mixer was changed as shown in Table 1.

TABLE 1 Comp. <<Composition>> Comp. Ex. 1 Ex. 2 Ex. 1 Ex. 2 Ex. 3 NCOequivalent weight of PP 466.0 540.0 540.0 540.0 540.0 Prepolymer 2,4-TDI(parts) 316 286 286 286 286 (1st component) Hydrogenated MDI (parts) 88PTMG 1000 (parts) 539 714 714 714 714 DEG (parts) 57 Chain extender (2ndLiquid MOCA (parts) component) Solid MOCA (parts) 256 106 168 186 190Aqueous dispersion Three-functional PPG 3000 38 42 43 43 (3rd component)(parts) Water (parts) 8 3 2 2 TOYOCAT-ET (parts) 1 1 1 1 Silicone-basedsurfactant 1 1 1 1 SH-193 (parts) Air loading rate (L/min.) 18.2 18.218.2 18.2 <<Physical Hard segment content 38 31 31 31 31 properties>>(HSC) (%) Density D (g/cm³) 0.80 0.22 0.33 0.38 0.40 Y value (=HSC +65 * D) 90 46 53 56 57 S value 1.00 0.97 0.97 0.97 0.97 Type A hardness(°) 80 16 31 42 48 Type D hardness (°) 57 3 15 25 32 Average celldiameter d 30 190 162 149 143 (μm) Number of cells/mm² 480 20 31 35 39E′₄₀ (MPa) (40° C.) 299 1 5 9 11 Thickness (mm) 1.25 1.34 1.35 1.34 1.34Polishing test Polishing rate (nm/min) 229.7 168.8 231.2 229.4 232(Good) (Poor) (Good) (Good) (Good) Polishing uniformity 12.7 9.0 6.8 4.64.8 (CV %) (Poor) (Poor) (Good) (Good) (Good) Presence or absence ofPresent (2) Absent Absent Absent Absent scratches (in 5 substrates)(Poor) (0) (0) (0) (0) (Good) (Good) (Good) (Good) <<Composition>> Ex. 4Comp. Ex. 3 Comp. Ex. 4 Comp. Ex. 5 NCO equivalent weight of PP 540.0540.0 540.0 540.0 Prepolymer 2,4-TDI (parts) 286 286 286 286 (1stcomponent) Hydrogenated MDI (parts) PTMG 1000 (parts) 714 714 714 714DEG (parts) Chain extender (2nd Liquid MOCA (parts) component) SolidMOCA (parts) 204 208 212 215 Aqueous dispersion Three-functional PPG3000 44 45 45 45 (3rd component) (parts) Water (parts) 1 1 0 0TOYOCAT-ET (parts) 1 1 1 1 Silicone-based surfactant 1 1 1 1 SH-193(parts) Air loading rate (L/min.) 18.2 18.2 18.2 18.2 <<Physical Hardsegment content 31 31 31 31 properties>> (HSC) (%) Density D (g/cm³)0.50 0.61 0.68 0.73 Y value (=HSC + 65 * D) 64 71 75 78 S value 0.970.97 0.97 0.97 Type A hardness (°) 55 73 82 85 Type D hardness (°) 34 5058 60 Average cell diameter d 129 119 97 89 (μm) Number of cells/mm² 4149 69 79 E′₄₀ (MPa) (40° C.) 20 31 48 46 Thickness (mm) 1.32 1.34 1.351.34 Polishing test Polishing rate (nm/min) 228.1 220.8 220.2 211.9(Good) (Good) (Good) (Good) Polishing uniformity 5.3 8.6 10.6 11.7 (CV%) (Good) (Poor) (Poor) (Poor) Presence or absence of Absent Absent (0)Present (3) Present scratches (in 5 substrates) (0) (Good) (Poor) (3)(Poor) (Good) *In Comparative Example 1, 2% by weight of Expancel 551 DEwas added as a blowing agent. *Liquid MOCA means a liquid mixture ofPTMG and crude MOCA (multimer content: 40% by mass) at a mass ratio of1:1.

Examples 5 to 9 and Comparative Examples 6 to 8

Next, various polishing layers having different densities weremanufactured by using a liquid MOCA, and by changing the ratio ofcomponents as shown in Table 2.

Example 5

In Example 5, as a first component, which was a prepolymer, anisocyanate group-containing urethane prepolymer having an isocyanatecontent of 7.8% and an NCO equivalent weight of 540 was used. Theprepolymer was obtained by reacting 2,4-TDI (286 parts) and the PTMG(714 parts) having a number average molecular weight of approximately1000. This prepolymer was heated to 55° C., and degassed under reducedpressure. As a second component, which was a chain extender, the liquidMOCA (234 parts) was degassed under reduced pressure. A third component,an aqueous dispersion, was obtained by mixing the three-functional PPG(41 parts) having a number average molecular weight of 3000, water (3parts), a catalyst (TOYOCAT-ET manufactured by Tosoh Corporation) (1part), and a silicone-based surfactant (SH-193 manufactured by DowCorning Corporation) (4 parts) with each other with stirring. Then, theaqueous dispersion was degassed under reduced pressure. The firstcomponent, the second component, and the third component were suppliedto a mixer at a weight ratio of 1000 parts:234 parts:49 parts and at aflow rate of 80 kg/min. Here, air was supplied into the mixer at a flowrate of 19.1 L/min through nozzles provided to a stirring rotor(specifically, 19.1 L or air was supplied per 80 kg of the total of thefirst to third components). The obtained mixture liquid was poured intoa mold, and cured at 100° C. for 5 hours. Then, the formed polyurethaneresin foam was taken out of the mold. This foam was sliced into sheetshaving a thickness of 1.28 mm. Thus, urethane sheets were fabricated,and polishing pads were obtained.

Examples 6 to 9 and Comparative Examples 6 to 8

Polishing pads having thicknesses of 1.28 to 1.30 mm were obtained inthe same manner as in Example 5, except that the ratio of componentssupplied to the mixer was changed as shown in Table 2.

TABLE 2 <<Composition>> Comp. Ex. 6 Ex. 5 Ex. 6 Ex. 7 NCO equivalentweight of PP 540.0 540.0 540.0 540.0 Prepolymer 2,4-TDI (parts) 286 286286 286 (1st component) Hydrogenated MDI (parts) PTMG 1000 (parts) 714714 714 714 DEG (parts) Chain extender (2nd Liquid MCCA (parts) 153 234273 281 component) Solid MOCA (parts) Aqueous dispersionThree-functional PPG 3000 37 41 42 43 (3rd component) (parts) Water(parts) 7 3 2 1 TOYOCAT-ET (parts) 1 1 1 1 Silicone-based surfactant 4 44 4 SH-193 (parts) Air loading rate (L/min.) 19.1 19.1 19.1 19.1<<Physical Hard segment content (HSC) 32 30 29 29 properties>> (%)Density D (g/cm³) 0.12 0.33 0.39 0.41 Y value (=HSC + 65 * D) 40 51 5455 S value 0.74 0.73 0.72 0.72 Type A hardness (°) 10 22 25 31 Type Dhardness (°) 4 6 8 11 Average cell diameter d 224 178 168 158 (μm)Number of cells/mm² 15 25 28 30 E′₄₀ (MPa) (40° C.) 1 2 2 2 Thickness(mm) 1.29 1.28 1.30 1.28 Polishing test Polishing rate (nm/min) 181.2211.1 213.4 218.6 (Poor) (Good) (Good) (Good) Polishing uniformity (CV%) 11.2 (Poor) 7.6 (Fair) 4.6 (Good) 4.2 (Good) Presence or absence ofPresent (1) Absent (0) Absent (0) Absent (0) scratches (in 5 substrates)(Poor) (Good) (Good) (Good) <<Composition>> Ex. 8 Ex. 9 Comp. Ex. 7Comp. Ex. 8 NCO equivalent weight of PP 540.0 540.0 540.0 540.0Prepolymer 2,4-TDI (parts) 286 286 286 286 (1st component) HydrogenatedMDI (parts) PTMG 1000 (parts) 714 714 714 714 DEG (parts) Chain extender(2nd Liquid MCCA (parts) 290 295 301 304 component) Solid MOCA (parts)Aqueous dispersion Three-functional PPG 3000 43 43 43 44 (3rd component)(parts) Water (parts) 1 1 0 0 TOYOCAT-ET (parts) 1 1 1 1 Silicone-basedsurfactant 4 4 4 4 SH-193 (parts) Air loading rate (L/min.) 19.1 19.119.1 19.1 <<Physical Hard segment content (HSC) 28 28 28 28 properties>>(%) Density D (g/cm³) 0.49 0.54 0.69 0.75 Y value (=HSC + 65 * D) 60 6373 77 S value 0.71 0.71 0.71 0.70 Type A hardness (°) 47 53 78 85 Type Dhardness (°) 27 33 54 60 Average cell diameter d 142 123 96 88 (μm)Number of cells/mm² 35 45 69 80 E′₄₀ (MPa) (40° C.) 4 10 36 48 Thickness(mm) 1.29 1.28 1.30 1.28 Polishing test Polishing rate (nm/min) 221.1217.3 212.2 201.2 (Good) (Good) (Good) (Good) Polishing uniformity (CV%) 4.3 (Good) 7.8 (Fair) 10.3 (Poor) 10.9 (Poor) Presence or absence ofAbsent (0) Absent (0) Present (3) Present (3) scratches (in 5substrates) (Good) (Good) (Poor) (Poor)

Examples 10 to 15 and Comparative Examples 9 to 13

Finally, polishing layers were manufactured by increasing or decreasingthe amounts of the polyisocyanate compound, the polyol compound, and thepolyamine compound.

Example 10

In Example 10, as a first component, which was a prepolymer, anisocyanate group-containing urethane prepolymer having an isocyanatecontent of 10.0% and an NCO equivalent weight of 420 was used. Theprepolymer was obtained by reacting 2,4-TDI (325 parts) and the PTMG(675 parts) having a number average molecular weight of approximately1000. This prepolymer was heated to 55° C., and degassed under reducedpressure. As a second component, which was a chain extender, the liquidMOCA (397 parts) was degassed under reduced pressure. A third component,an aqueous dispersion, was obtained by mixing the three-functional PPG(43 parts) having a number average molecular weight of 3000, water (1part), a catalyst (TOYOCAT-ET manufactured by Tosoh Corporation) (1part), and a silicone-based surfactant (SH-193 manufactured by DowCorning Corporation) (4 parts) with each other with stirring. Then, theaqueous dispersion was degassed under reduced pressure. The firstcomponent, the second component, and the third component were suppliedto a mixer, at a weight ratio of 1000 parts:397 parts:49 parts and at aflow rate of 80 kg/min. Here, air was supplied into the mixer at a flowrate of 19.1 L/min. The obtained mixture liquid was poured into a moldand cured. Then, the formed polyurethane resin foam was taken out of themold. This foam was sliced into sheets having a thickness of 1.27 mm.Thus, urethane sheets were fabricated, and polishing pads were obtained.

Examples 11 to 15 and Comparative Examples 9 to 13

In Examples 11 to 15 and Comparative Examples 9 to 18, polishing padshaving thicknesses of 1.27 to 1.30 mm were manufactured by the samemethod as in Example 10, except that the ratio of components was changedas shown in Table 3 or 4.

TABLE 3 Comp. Ex. <<Composition>> Comp. Ex. 9 10 Ex. 10 Ex. 11 NCOequivalent weight of PP 340.0 380.0 420.0 460.0 Prepolymer 2,4-TDI(parts) 367 344 325 310 (1st component) Hydrogenated MDI (parts) PTMG1000 (parts) 634 656 675 690 DEG (parts) Chain extender (2nd Liquid MOCA(parts) 519 452 397 352 component) Solid MOCA (parts) Aqueous dispersionThree-functional PPG 3000 43 43 43 43 (3rd component) (parts) Water(parts) 2 1 1 1 TOYOCAT-ET (parts) 1 1 1 1 Silicone-based surfactant 4 44 4 SH-193 (parts) Air loading rate (L/min.) 19.1 19.1 19.1 19.1<<Physical Hard segment content (HSC) 38 35 33 32 properties>> (%)Density D (g/cm³) 0.50 0.47 0.46 0.43 Y value (=HSC + 65 * D) 70 66 6360 S value 0.72 0.72 0.72 0.72 Type A hardness (°) 67 56 48 41 Type Dhardness (°) 45 35 28 20 Average cell diameter d (μm) 132 142 145 156Number of cells/mm² 39 37 33 31 E′₄₀ (MPa) (40° C.) 138 55 29 13Thickness (mm) 1.29 1.30 1.27 1.29 Polishing test Polishing rate(nm/min) 187.5 192.4 194.6 203.3 (Poor) (Fair) (Fair) (Good) Polishinguniformity (CV %) 11.8 7.5 (Fair) 6.5 (Good) 5.7 (Good) (Poor) Presenceor absence of Present Absent (0) Absent (0) Absent (0) scratches (in 5substrates) (2) (Poor) (Good) (Good) (Good) <<Composition>> Ex. 12 Ex.13 Ex. 14 Ex. 15 NCO equivalent weight of PP 500.0 540.0 580.0 620.0Prepolymer 2,4-TDI (parts) 297 286 276 268 (1st component) HydrogenatedMDI (parts) PTMG 1000 (parts) 703 714 724 732 DEG (parts) Chain extender(2nd Liquid MOCA (parts) 314 281 253 221 component) Solid MOCA (parts)Aqueous dispersion Three-functional PPG 3000 43 43 43 43 (3rd component)(parts) Water (parts) 1 1 1 1 TOYOCAT-ET (parts) 1 1 1 1 Silicone-basedsurfactant 4 4 4 4 SH-193 (parts) Air loading rate (L/min.) 19.1 19.119.1 19.1 <<Physical Hard segment content (HSC) 30 29 27 26 properties>>(%) Density D (g/cm³) 0.41 0.39 0.36 0.37 Y value (=HSC + 65 * D) 57 5451 50 S value 0.72 0.72 0.72 0.72 Type A hardness (°) 36 25 23 22 Type Dhardness (°) 16 11 8 6 Average cell diameter d (μm) 161 168 170 168Number of cells/mm² 31 28 28 27 E′₄₀ (MPa) (40° C.) 4 2 1 1 Thickness(mm) 1.28 1.28 1.30 1.29 Polishing test Polishing rate (nm/min) 208.4218.6 214.2 215.2 (Good) (Good) (Good) (Good) Polishing uniformity (CV%) 4.7 (Good) 4.2 (Good) 5.8 (Good) 7.5 (Fair) Presence or absence ofAbsent (0) Absent (0) Absent (0) Absent (0) scratches (in 5 substrates)(Good) (Good) (Good) (Good)

TABLE 4 <<Composition>> Comp. Ex. 11 Comp. Ex. 12 Comp. Ex. 13 NCOequivalent weight of PP 680.0 720.0 760.0 Prepolymer 2,4-TDI (parts) 257251 246 (1st component) Hydrogenated MDI (parts) PTMG 1000 (parts) 743749 754 DEG (parts) Chain extender (2nd Liquid MOCA (parts) 198 180 164component) Solid MOCA (parts) Aqueous dispersion Three-functional PPG3000 43 43 43 (3rd component) (parts) Water (parts) 1 1 1 TOYOCAT-ET(parts) 1 1 1 Silicone-based surfactant 4 4 4 SH-193 (parts) Air loadingrate (L/min.) 19.1 19.1 19.1 <<Physical Hard segment content (HSC) (%)25 24 23 properties>> Density D (g/cm³) 0.31 0.29 0.26 Y value (=HSC +65*D) 45 43 40 S value 0.72 0.72 0.72 Type A hardness (°) 18 12 10 TypeD hardness (°) 4 2 1 Average cell diameter d (μm) 182 187 192 Number ofcells/mm² 24 23 23 E′₄₀ (MPa) (40° C.) 1 1 0 Thickness (mm) 1.30 1.281.27 Polishing test Polishing rate (nm/min) 216.3 (Good) 201.1 (Good)175.3 (Poor) Polishing uniformity (CV %)   9.4 (Poor)  10.3 (Poor)  12.2(Poor) Presence or absence of Absent Absent Absent scratches (in 5substrates) (0) (Good) (0) (Good) (0) (Good)

<Physical Properties Evaluation>

For each of Examples and Comparative Examples described above, the hardsegment content (%), the density (g/cm³), the Y value, the type Ahardness (°), the type D hardness (°), the average cell diameter (μm),the number of cells per square millimeter, the storage elastic modulusE′40 (MPa), and the thickness (mm) were calculated or measured. Tables 1to 4 show the results.

Note that methods for measuring these items were as follows.

The density (g/cm³) was calculated by measuring the weight (g) of asample cut into a piece having a predetermined size, and finding thevolume (cm³) from the size.

The type A hardness was measured according to Japanese IndustrialStandards Committee (JIS K 7311) by using a Shore A durometer. Note thatthe total thickness of each sample was set to at least 4.5 mm or more,by stacking four sheets of the urethane sheets (thickness: approximately1.3 mm) described in each of Comparative Examples and Examples.

The type D hardness was measured according to JIS K 6253-1997/ISO 7619by using a type D durometer manufactured by TECLOCK corporation. Notethat the total thickness of each sample was set to at least 4.5 mm ormore by stacking four sheets of the urethane sheets (thickness:approximately 1.3 mm) described in each of Comparative Examples andExamples.

The average cell diameter (μm) and the number of cells per squaremillimeter were determined as follows. Specifically, an area ofapproximately 1.3 mm square on the pad surface was observed in anenlarged manner with a microscope (VH-6300 manufactured by KEYENCE) witha magnification of 175. The obtained image was binarized with imageprocessing software (Image Analyzer V20 LAB Ver. 1.3 manufactured byNikon Corporation). The number of cells was counted, and the equivalentcircle diameters and the average value (average cell diameter) thereofwere calculated from the areas of the cells. Note that noise componentswere removed by setting the cutoff value (lower limit) of the celldiameters to 10 μm.

As the storage elastic modulus (E′₄₀ (MPa)) at 40° C., the storageelastic modulus was measured with RSAIII of TA Instruments. Japan.according to JIS K 7244-4 with an initial load of 10 g, a strain rangeof 0.01 to 4%, and a measuring frequency of 0.2 Hz at 40° C.

<Polishing Test>

The polishing pad of each of Examples and Comparative Examples waspolished under the following polishing conditions, and the polishingrate, the polishing uniformity, and the presence or absence of scratcheswere observed. As workpieces, substrates (uniformity (CV %): 13%) inwhich insulating films having a thickness of 1 μm were formed by CVDfrom tetraethoxysilane on 12-inch silicon wafers were used.

(Polishing Rate)

As the polishing rate, the amount of polishing per minute is representedby the thickness (nm). Before and after the polishing, the thicknessesof the insulating film of each substrate were measured at 17 sites, andthe average value was determined from the measurement results. Notethat, the thicknesses were measured with an optical film-thickness andfilm quality measuring apparatus (ASET-F5x manufactured by KLA-TencorCorporation) in the DBS mode.

(Polishing Uniformity)

The polishing uniformity was determined based on the dispersion(standard deviation/average value) of the measurement results of theabove-described thicknesses at the 17 sites.

(Presence or Absence of Scratches)

In the evaluation of scratches, 25 substrates were sequentially polishedrepeatedly three times. After the polishing, 5 substrates, namely, 21stto 25th substrates, were measured with an unpatterned wafer surfaceinspection system (Surfscan SP1DLS manufactured by KLA-TencorCorporation) in the high sensitivity measurement mode. Thus, thepresence or absence of scratches on the substrate surface was evaluated.

Note that the polishing conditions employed in the above-described testwere as follows.

Polishing machine used: F-REX300 manufactured by EBARA CORPORATION.

Number of revolutions: 70 rpm (platen), 71 rpm (top ring).

Polishing pressure: 220 hPa.

Polishing agent: Product No: SS25 manufactured by Cabot Corporation (amixture liquid of undiluted SS25:pure water=1:1 was used).

Polishing agent temperature: 30° C.

Amount of polishing agent discharged: 200 ml/min.

Workpiece used: a substrate in which an insulating film having athickness of 1 μm was formed from tetraethoxysilane by CVD on a siliconwafer having a diameter of 12 inches.

Polishing time: 60 seconds/each time.

Dressing: (after a polishing cloth was attached) 10 minutes.

Tables 1 to 4 show the results of the polishing test conducted on eachof Examples and Comparative Examples by using the above-describedmethods.

Here, since the polishing pad of the present invention needs to exhibitthe effects of the polishing rate, the polishing uniformity, and thescratch reduction in a balanced manner, the results of the polishingtest were evaluated as follows, in consideration of the values as aproduct.

A polishing rate of 200 (nm/min) or higher was evaluated as Good, apolishing rate from 190 inclusive to 200 exclusive (nm/min) wasevaluated as Fair, and a polishing rate of less than 190 (nm/min) wasevaluated as Poor.

A polishing uniformity of 7.0 (CV %) or less was evaluated as Good, apolishing uniformity from 7.0 exclusive to 8.0 inclusive (CV %) wasevaluated as Fair, and a polishing uniformity exceeding 8.0 (CV %) wasevaluated as Poor.

Regarding the presence or absence of scratches, a case where scratcheswere absent (0) was evaluated as Good, and a case where (one or more)scratches were present was evaluated as Poor.

Then, among the three items of the polishing rate, the polishinguniformity, and the presence or absence of scratches, polishing padsevaluated as Fair in terms of none of or one of the three items(polishing pads evaluated as Good in terms of all the three items, andpolishing pads evaluated as Good in terms of two items and Fair in termsof one item) were evaluated as preferable examples (Examples), whereassamples evaluated as Fair in terms of two or more items and samplesevaluated as Poor in terms of at least one item were evaluated asunfavorable examples (Comparative Examples) in the present invention.

Test Result 1 Comparative Example 1

The conventional polishing pad manufactured in Comparative Example 1where neither air was blown nor the aqueous dispersion was used had ahigh density and a high hard segment content. In addition, the polishingpad had a structure having a large number of cells per square millimeterand a small average cell diameter, i.e., a structure in which anuncountable number of very small cells were present (see the photographon the right in FIG. 1). As a result, scratches were formed, and theobtained numeric value of the polishing uniformity was alsounsatisfactory.

Test Result 2 Examples 1 to 4 and Comparative Examples 2 to 5

Here, Examples 1 to 4 and Comparative Examples 2 to 5 in which the solidMOCA was used as the chain extender are discussed. In the case where theamount of water added was large and the amount of the solid MOCA wassmall, the density was too small, and the results of the polishing rateand the polishing uniformity were poor (Comparative Example 2). On theother hand, in the case where the amount of water added was small andthe mount of the solid MOCA was large, the density was high, and hencescratches were formed, and the result of the polishing uniformity wasalso insufficient (Comparative Examples 3 to 5).

Meanwhile, in the case of the polishing pads manufactured with theamounts of the solid MOCA and water added being adjusted, so that thedensity and the hard segment content fell within the ranges of thepresent invention, no scratches were formed, and the results of both thepolishing rate and the polishing uniformity were good (Examples 1 to 4).

Test Result 3 Examples 5 to 9 and Comparative Examples 6 to 8

Examples 5 to 9 and Comparative Examples 6 to 8 in which the liquid MOCAwas used as the chain extender are discussed. In the case where theamount of water added was large and the amount of the liquid MOCA wassmall, the density was too low, and hence the obtained results wereinsufficient especially in terms of the polishing rate and the polishinguniformity (Comparative Example 6). On the other hand, when the amountof water added was small and the amount of the liquid MOCA was large,the density was high, and hence scratches were formed, and the result ofthe polishing uniformity was also poor (Comparative Examples 7 and 8).

Meanwhile, in the case of the polishing pads manufactured with theamounts of the liquid MOCA and water added being adjusted, so that thedensity and the hard segment content fell within the ranges of thepresent invention, no scratches were formed, and the obtained results ofboth the polishing rate and the polishing uniformity were good (Examples5 to 9).

Test Result 4 Examples 10 to 15 and Comparative Examples 9 to 13

Examples 10 to 15 and Comparative Examples 9 to 13 among which thecontent ratio of the polyisocyanate compound, the polyol compound, andthe polyamine compound was varied are discussed. In the case where theamount (equivalence ratio) of the polyamine compound was too largerelative to the amount of the polyol compound, the hard segment contentincreased excessively, so that two or more among scratch formation, alow polishing rate, and a low polishing uniformity occurred (ComparativeExamples 9 and 10).

In contrast, in the case where the amount (equivalence ratio) of thepolyamine compound was too small relative to the amount of the polyolcompound, the hard segment content decreased excessively, so that theresults of especially the polishing rate and the polishing uniformitywere very poor (Comparative Examples 11 to 18).

Meanwhile, in the case of the polishing pads manufactured with theequivalence ratio of the amino groups of the polyamine compound and thehydroxyl groups of the polyol compound for forming a prepolymer beingadjusted, so that the hard segment content and the density fell withinthe ranges of the present invention, no scratches were formed, and theobtained results of both the polishing rate and the polishing uniformitywere sufficiently good (Examples 10 to 15).

As is apparent from the above, in the case of the polishing pads ofExample 1 to 15 having hard segment contents in a range from 26 to 34%and densities D in a range from 0.30 to 0.60 g/cm³, no scratches wereformed on the polishing surfaces of the workpieces, and the obtainedresults of the polishing rate and the polishing uniformity were good.Hence, it was found that, in contrast to Comparative Examples 1 to 13,the effects on all the scratch reduction, the polishing rate, and thepolishing uniformity were exhibited in a balanced manner.

INDUSTRIAL APPLICABILITY

Since the polishing pad of the present invention has a low hard segmentcontent, the strong pressing is suppressed, and scars are less likely tobe formed. In addition, because of the high porosity (low density),scars due to clogging are also less likely to be formed. Moreover, sincethe polishing pad of the present invention is softer than polishing padshaving polishing layers molded by conventional dry methods, thepolishing pad is excellent also in polishing rate and polishinguniformity. Meanwhile, since the polishing pad of the present inventionis dry-molded, the polishing pad has a lower wearing rate of thepolishing surface than the wet-molded polishing pads. Hence, thepolishing pad of the present invention can retain a constant polishingstate for a long period. Accordingly, although dry-molded, the polishingpad of the present invention can be advantageously used for both primaryprocessing and finish processing. Therefore, the polishing pad of thepresent invention and the manufacturing method therefor have industrialapplicability.

1. A polishing pad for polishing a semiconductor device, comprising apolishing layer having a polyurethane-polyurea resin foam containingsubstantially spherical cells, wherein the polyurethane-polyurea resinfoam has a hard segment content (HSC) in a range from 26 to 34%, and thepolyurethane-polyurea resin foam has a density D in a range from 0.30 to0.60 g/cm³, the hard segment content (HSC) being determined by thefollowing formula (1):HSC=100×(r−1)×(Mdi+Mda)÷(Mg+r×Mdi+(r−1)×Mda)  (1), wherein Mdirepresents an average molecular weight of a polyisocyanate compound(s)constituting the polyurethane-polyurea resin per two isocyanatefunctional groups; Mg represents an average molecular weight of a polyolcompound(s) constituting the polyurethane-polyurea resin per twohydroxyl functional groups; Mda represents an average molecular weightof a polyamine compound(s) constituting the polyurethane-polyurea resinper two amino functional groups; and r represents the equivalence ratioof isocyanate groups of the polyisocyanate compound(s) constituting thepolyurethane-polyurea resin to hydroxyl groups of the polyol compound(s)constituting the polyurethane-polyurea resin.
 2. The polishing padaccording to claim 1, wherein the polyurethane-polyurea resin foam has aY value in a range from 50 to 65, the Y value being determined byY=HSC+65×D, wherein D represents a density (g/cm³) and HSC is the valuedetermined by the formula (1).
 3. The polishing pad according to claim1, wherein the polyurethane-polyurea resin foam has an average celldiameter of 120 to 185 μm.
 4. The polishing pad according to claim 1,wherein the polyurethane-polyurea resin foam has a type A hardness of 20to 55 degrees.
 5. The polishing pad according to claim 1, wherein thepolyurethane-polyurea resin foam has a type D hardness of 5 to 35degrees.
 6. The polishing pad according to claim 1, wherein thepolyurethane-polyurea resin foam has a storage elastic modulus E′ of 1to 30 MPa, the storage elastic modulus E′ being measured at 40° C. withan initial load of 10 g, a strain range of 0.01 to 4%, and a measuringfrequency of 0.2 Hz in a tensile mode.
 7. The polishing pad according toclaim 1, wherein a layer harder than the polishing layer is laminated ona surface of the polishing layer, the surface being opposite from apolishing surface of the polishing layer.
 8. A method for manufacturingthe polishing pad according to claim 1, the method comprising: aprovision step of providing an isocyanate group-containing compound (A),a polyisocyanate compound (B), a polyamine compound (D), a mixtureliquid (E) comprising water, a foam stabilizer, and a reaction catalyst,and a gas non-reactive with all the components; a mixing step of mixingat least the isocyanate group-containing compound (A), thepolyisocyanate compound (B), the polyamine compound (D), the mixtureliquid (E) comprising the water, the foam stabilizer, and the reactioncatalyst, and the gas non-reactive with all the components with eachother to obtain a mixture liquid for molding a foam; a foam-molding stepof molding a polyurethane-polyurea resin foam from the mixture liquidfor molding a foam; and a polishing layer formation step of forming apolishing layer having a polishing surface for polishing a workpiecefrom the polyurethane-polyurea resin foam.
 9. The method formanufacturing the polishing pad according to claim 8, wherein in theprovision step, a polyol compound (C-2) is further provided, and in themixing step, the polyol compound (C-2) is mixed.
 10. The method formanufacturing the polishing pad according to claim 9, wherein in theprovision step, the polyamine compound (D) and the polyol compound (C-2)are provided, with the equivalence ratio of amino groups of thepolyamine compound (D) to the sum of the chemical equivalents of aminogroups of the polyamine compound (D) and hydroxyl groups of the polyolcompound (C-2) (the chemical equivalent of active hydrogen groups) being0.70 to 0.97 (the amino groups/(the amino groups+the hydroxyl groups)).11. The method for manufacturing the polishing pad according to claim 8,wherein the polyamine compound (D) is a crudemethylenebis(o-chloroaniline) (MOCA) which is a mixture of monomer andmultimers of MOCA and which contains the multimers in an amount of 15%by mass or more.
 12. The method for manufacturing the polishing padaccording to claim 9, wherein the polyol compound (C-2) ispoly(tetramethylene glycol) or poly(propylene glycol) having a numberaverage molecular weight of 500 to 5000, or a mixture thereof.